Herein are disclosed fuser members useful in electrostatographic reproducing apparatuses, including digital, image on image, and contact electrostatic printing apparatuses. The present fuser members can be used as fuser members, pressure members, transfuse or transfix members, and the like. In an embodiment, the fuser members comprise an outer layer comprising a fluoroelastomer. In embodiments, the outer layer of the fuser member is prepared by addition of a polydimethylsiloxane additive in a process for coating a fuser member.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member, and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles and pigment particles, or toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support, which may be the photosensitive member itself, or other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known. To fuse electroscopic toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner material to be firmly bonded to the support.
Typically, the thermoplastic resin particles are fused to the substrate by heating to a temperature of between about 90 to about 200° C. or higher depending upon the softening range of the particular resin used in the toner. It may be undesirable; however, to increase the temperature of the substrate substantially higher than about 250° C. because of the tendency of the substrate to discolor or convert into fire at such elevated temperatures, particularly when the substrate is paper.
Several approaches to thermal fusing of electroscopic toner images have been described. These methods include providing the application of heat and pressure substantially concurrently by various means, a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat may be applied by, heating one or both of the rolls, plate members, or belt members. The fusing of the toner particles takes place when the proper combinations of heat, pressure and contact time are provided. The balancing of these parameters to bring about the fusing of the toner particles is well known in the art, and can be adjusted to suit particular machines or process conditions.
During operation of a fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between the roll pair, or plate or belt members. The concurrent transfer of heat and the application of pressure in the nip affect the fusing of the toner image onto the support. It is important in the fusing process that no offset of the toner particles from the support to the fuser member takes place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the background or interfering with the material being copied there. The referred to “hot offset” occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser roll, and accordingly it is desired to provide a fusing surface, which has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser roll, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, nonfunctional silicone oils or mercapto- or amino-functional silicone oils, to prevent toner offset.
U.S. Pat. No. 4,515,884 to Field et al. discloses a fuser member having a silicone elastomer-fusing surface, which is coated with a toner release agent, which includes an unblended polydimethyl siloxane.
U.S. Pat. No. 6,197,989 B1 to Furukawa et al. discloses a fluorine-containing organic silicone compound represented by a formula.
U.S. Pat. No. 5,736,250 teaches a crosslinked polysiloxane and fluoroelastomer layer.
U.S. Pat. No. 5,716,747 to Uneme et al. discloses a fluororesin coated fixing device with a coating of a fluorine containing silicone oil.
U.S. Pat. No. 5,698,320 to Ebisu et al. discloses a fixing device coated with a fluororesin, and having a fluorosilicone polymer release agent.
U.S. Pat. No. 5,641,603 to Yamazaki et al. discloses a fixing method using a silicone oil coated on the surface of a heat member.
U.S. Pat. No. 5,636,012 to Uneme et al. discloses a fixing device having a fluororesin layer surface, and using a fluorine-containing silicone oil as a repellant oil.
U.S. Pat. No. 5,627,000 to Yamazaki et al. discloses a fixing method having a silicone oil coated on the surface of the heat member, wherein the silicone oil is a fluorine-containing silicone oil and has a specific formula.
U.S. Pat. No. 5,624,780 to Nishimori et al. discloses a fixing member having a fluorine-containing silicone oil coated thereon, wherein the silicone oil has a specific formula.
U.S. Pat. No. 5,568,239 to Furukawa et al. discloses a stainproofing oil for heat fixing, wherein the fluorine-containing oil has a specific formula.
U.S. Pat. No. 5,463,009 to Okada et al. discloses a fluorine-modified silicone compound having a specific formula, wherein the compound can be used for oil-repellency in cosmetics.
U.S. Pat. No. 4,968,766 to Kendziorski discloses a fluorosilicone polymer for coating compositions for longer life.
Known processes for providing surfaces of fuser members include dipping the substrate into a bath of coating solution or spraying the periphery of the substrate with the coating material. Another process for providing surfaces of fuser members involves dripping material spirally over a horizontally rotating cylinder. Generally, in this flow coating method, the coating is applied to the substrate by rotating the substrate in a horizontal position about a longitudinal axis and applying the coating from an applicator to the substrate in a spiral pattern in a controlled amount so that substantially all the coating that exits the applicator adheres to the substrate. For specific details of an embodiment of the flow coating method, attention is directed to U.S. Pat. No. 5,945,223, entitled “Flow Coating Solution and Fuser Member Layers Prepared Therewith” and to U.S. Pat. No. 6,408,753 and U.S. Pat. No. 6,521,330, entitled “Flow Coating Process for Manufacture of Polymeric Printer and Belt Components,” and to U.S. Pat. No. 6,479,158, entitled “Fuser Member with an Amino Silane Adhesive Layer and Preparation Thereof,” the disclosures of which are hereby incorporated by reference in their entirety. For specific details of an embodiment of fuser roll top coat compositions, attention is directed to U.S. Pat. No. 5,332,641, entitled “Fuser Member with an Amino Silane Adhesive Layer,” the disclosure of which is hereby incorporated by reference in its entirety.
However, not all coatings are compatible with the flow coating method. Specifically, only materials that can be completely dissolved in a solvent can be flow coated. Further, it is desirable that the material have the ability to stay dissolved during the entire flow coating process which may take up to approximately 8 hours or longer, and must stay dissolved during the manufacturing period which may be up to several days. Good results are not obtained with materials which tend to coagulate or crystallize within the time period required for flow coating, which may be on the order of about 8 hours and for production manufacturing, may be on the order of a few days, for example, from about 1 to about 4 days. It is desirable to use a material capable of being flow coated for an increased amount of time to enable flow coating in a manufacturing and production environment. It is very costly to periodically shut down a manufacturing line and change the solution delivery system. If the coating does not have the desired properties, the assembly line may need to be shut down often, for example, every hour or every few hours in order to clean the delivery line of coagulated or crystallized material. Therefore, it is desirable to use a material that has good flow coating properties in order to allow for manufacturing to continue for a long period of time, for example several days, without incurring the above problems in the procedure.
It is also desirable that the coating be slow drying to avoid trapping solvent in the under layers which tends to cause bubbles and solvent “pops.” Bubbles result from trapped air in the coating which results in non-uniformity of coating and or surface defects. Solvent “pops” are defined as trapped air or solvent voids that rupture resulting in crater-like structures causing non-uniform coated areas or surface defects. In either case, these defects can act as initiation sites for adhesion failures.
Moreover, useful materials for the flow coating process must possess the ability to flow in a manner that allows for the entire roll to be coated. Therefore, it is desirable that the material possess a desired viscosity which allows it to flow over the entire surface of the member being coated. Along with these properties, it is desirable that the material-to be coated possess a balance between viscosity and percent solids. Similarly, it is desirable that the coating material have the ability to completely dissolve in a solvent in order to prevent precipitation of the material that can lead to non-uniform flow coating, and imperfections in the final flow coated surface.
The balance between viscosity and percent solids is desired to enable sufficient build rates, which impact throughput and work in process. Build rates are defined as the thickness of a material that can be coated per unit time. The thickness of the material should allow for a balance between maintaining thickness uniformity and avoiding solvent “pops” and air bubbles. Throughput in the process is the number of units that are processed per unit time. Work in process is the number of units currently in any one of the process stages from beginning to end. The objective is to maximize the build rate and reduce the throughput time and work in process.
Many materials are known to be useful for outer coatings of a fuser member, such as for example, silicone rubbers, fluoropolymers and fluoroelastomers, which possess some of the above qualities necessary for flow coating. However, problems may result once the fluoroelastomer is dissolved in a solvent and crosslinking or curing agents are added. For example, the curative or crosslinking agents tend to precipitate within minutes after addition to the solvent solutions. The precipitate causes numerous problems such as clogging the filters and pumps used in the flow coating process. Further, the entire fuser member cannot be coated due to early precipitation of the curing and/or crosslinking agent. In addition, early precipitation may lead to non-uniform flow coating and imperfections in the final flow coated surface. A flow coating solution that minimizes these deficiencies is described in U.S. Pat. No. 5,945,223.
Fuser member layers produced by the flow coating process sometimes exhibit additional defects that may occur particularly when the coatings are very thin, for example less than 50 micrometers in thickness. These defects include “snowflake agglomerates,” due to agglomeration of particles such as barium sulfate added to certain fluoroelastomers to prevent the fluoroelastomer pellets from sticking together, and “fisheyes,” which are typically 1 to 5 millimeter regions either devoid of a fluoroelastomer layer, or with a very thin fluoroelastomer layer. Such defects in the fuser member layer can cause undesirable image defects on the printed copy, such as toner spots, toner picking (i.e., removal of toner leaving white spots), non-uniform gloss, hot offset, and poor image permanence. There exists a need for a flow coating solution that forms a fuser member layer surface that is smooth and free or substantially free of such defects.
U.S. Pat. No. 4,571,371 discloses silicone used as a leveling agent in photoreceptor transport layers.
U.S. Pat. Nos. 5,750,204, 5,753,307, 5,700,568 and 5,695,878 to Badesha, et al. teach formulations for fluoroelastomer fuser outer member surfaces using an amino silane as a crosslinking agent.
U.S. Pat. No. 5,595,823 to Chen, et al., U.S. Pat. Nos. 5,729,813 and 6,159,588 to Eddy, et al., and U.S. Pat. No. 6,395,444 to Riehle, et al. disclose fluoroelastomer fuser outer layer compositions for high thermal conductivity.
U.S. Pat. No. 5,547,759 to Chen, et al., discloses formulations for fluoroelastomer coatings for fuser members.
U.S. Pat. Nos. 6,207,243, 6,114,041 and 5,935,712 to Tan, et al., disclose fuser member fluoroelastomer formulations with surface-treated thermally conductive fillers.
U.S. Pat. No. 6,696,158 to Chen, et al. discloses a fluorocarbon thermoplastic coating for fuser members.
U.S. Pat. No. 6,218,014 to Pickering, et al. discloses fluorocarbon fuser members with silicon carbide filler.
U.S. Pat. No. 6,514,650 to Schlueter, Jr. et al. teaches a thin perfluoropolymer outer coating for fuser members.
U.S. Pat. No. 6,721,529 to Chen, et al. discloses a fluoroelastomer coating composition for release agent donor members.
Currently, an acrylate copolymer with pendant glycol and perfluorooctane sulfonate groups has shown success in reducing snowflake agglomerates and fisheyes when used as a surfactant/leveling agent additive in fluoroelastomer coating solutions. However, this copolymer has been shown to demonstrate environmental persistence problems and can no longer be used. Use of other similar materials has resulted in the formation of fisheyes and/or snowflake agglomerates. Therefore, it is desired to provide a fluoroelastomer fuser member layer that reduces or eliminates surface defects, including fisheyes and snowflake agglomerates, and that performs well as a fuser member, and does not degrade other properties or desired features of the fuser member layer.